Method for torsional damping between a dynamometer and prime mover

ABSTRACT

A method for damping torsional vibration between a prime mover and the dynamometer with a torsional damping apparatus including a body plate rotatably coupled to a finger plate by a bearing, wherein the torsional damping apparatus interconnects the dynamometer and the prime mover. The finger plate includes a plurality of substantially radially outwardly protruding finger members engageable with a plurality of spring members at least partially disposed in corresponding recesses arranged about the rotation axis on the inner side of the body plate. An outer retainer ring removably coupled on the inner side of the body plate over the plurality of spring members for retaining the spring members in the corresponding recesses of the body plate. The finger members are engageable with the plurality of spring members to compress the plurality of spring members in response to relative rotational movement between the body plate and the finger plate about the rotation axis, wherein the spring members dampen torsional stress transmitted from the prime mover to the dynamometer.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a division of copending U.S. application Ser.No. 08/709,862 filed 10 Sept., 1996 and entitled "Dynamometer TorsionalDamping Apparatus and Method", assigned commonly herewith.

BACKGROUND OF THE INVENTION

The invention relates generally to torsional vibration damping, and moreparticularly to a dynamometer in combination with a damping apparatusfor damping torsional vibration between the dynamometer and a combustionengine, or prime mover.

Dynamometers are used generally for measuring the performance ofrotating machinery including combustion engines and drive trains, whichare alternatively referred to herein as prime movers. The automotiveindustry, for example, uses dynamometers to measure a variety ofparameters related to vehicle combustion engine performance includingoutput torque and horsepower during engine testing, which often lastsseveral hundreds of engine operating hours. The dynamometer testing isgenerally performed over engine operating speeds ranging between idleand maximum rated speed and under different loading conditions. Theadvent of smaller, lighter weight and more fuel efficient automotiveengines has resulted in a tendency toward higher engine operatingspeeds, which are required to perform the same as did larger predecessorengines. And in modern automotive engines, speeds range betweenapproximately 800 rpm at idle speed and up to approximately 10,000 rpm,which may be more or less depending on engine size and application.

In a typical engine dynamometer test configuration, an output shaft ofthe engine is coupled to an input shaft of the dynamometer. A rubberelement drive shaft section disposed, or interconnected, between thedynamometer and the engine isolates the dynamometer from engine inducedvibration, and in particular from torsional vibration resultingprimarily from pulses during combustion engine power strokes. One typeof rubber element drive shaft used commonly in these applications isavailable commercially from Dana Corporation, Toledo, Ohio under themark VIBRADAMPS™. Combustion engines operated at lower speeds havelonger durations between power strokes, and thus produce relatively moretorsional vibration and stress than engines operated at higher speeds.Similarly, engines with fewer cylinders produce relatively moretorsional stress than engines with greater numbers of cylinders, whichresults from the relatively increased duration between power strokes inengines having fewer cylinders. Many engines moreover have odd cylinderfiring patterns, which increases the amount of torsional vibrationtransmitted by the drive shaft.

At present, several different rubber element drive shafts are coupledinterchangeably between the engine and the dynamometer during the courseof engine performance testing. Each rubber element drive shaft hasdifferent damping characteristics for use during operation at differentengine speed ranges. The different rubber element drive shafts also varyin weight between approximately 45 and 75 pounds. At lower engineoperating speeds larger diameter, heavier weight rubber element driveshafts are required to absorb the relatively high torsional stresses,whereas at higher engine operating speeds smaller diameter, lighterweight and more rigid rubber element drive shafts are used.Interchanging these different rubber element drive shafts one or moretimes over the course of engine performance testing however is laboriousand time consuming work, which interrupts usually tight testingschedules. The installation must usually be performed by skilledtechnicians to ensure proper installation, which is required foraccurate test results and to prevent equipment damage. Also, the heavierweight rubber element drive shafts used in many lower speed operationsexceed the bearing load rating of many dynamometers.

Rubber elements shafts are rated in units of twist or deflection perunit of torque. Rubber element shafts have a tendency to deteriorate asa result of internal heating when subject to excessive stress, and theshafts may be irreversibly damaged by excessive stress lasting onlyseveral milliseconds. The use of an under-rated rubber element driveshaft in a particular dynamometer application therefore may result inthe destruction of the drive shaft, which is costly to replace. Inaddition, deterioration of a rubber element shaft may result in damageto the dynamometer. Rubber element drive shafts tends also to beinherently imbalanced as a result of the rubber element composition. Atlower engine speeds the adverse effect of the imbalance tends to benegligible, but at higher speeds the imbalanced drive shafts tend towobble or whip, which may damage equipment and pose a personnel safetyhazard. Furthermore, there tends to be substantial variation among thedamping and performance characteristics of commonly rated rubber elementdrive shafts, which adversely affects the consistency of measurementresults.

In view of the discussion above among other considerations, there existsa demonstrated need for an advancement in the art of dynamometertorsional damping.

It is therefore an object of the invention to provide a noveldynamometer torsional damping method that is economical and overcomeproblems with the prior art.

It is also an object of the invention to provide a novel dynamometerdamping method that is relatively lightweight, and is readily adaptablefor coupling to a variety of different dynamometers.

It is another object of the invention to provide a novel dynamometerdamping method for readily changing or adjusting the dampingcharacteristic for different dynamometer testing applications.

It is a further object of the invention to provide a novel dynamometerdamping method for damping torsional vibration and reducing stressbetween a dynamometer and a prime mover over a relatively wide range ofrotational operating speeds without changing the interchanging thedamping apparatus.

It is a yet another object of the invention to provide a novel methodfor a dynamometer with a body plate having a protruding central hubportion interconnected rotatably by an antifriction bearing to a fingerplate disposed about the protruding central hub portion, wherein theinterconnecting portions of the body plate and the finger pate have arelatively long axial dimension for improved mechanical integrity andperformance.

These and other objects, features and advantages of the presentinvention will become more fully apparent upon consideration of thefollowing Detailed Description of the Invention with the accompanyingDrawings, which may be disproportionate for ease of understanding,wherein like structure and steps are referenced by correspondingnumerals and indicators.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a engine dynamometer test arrangementaccording to an exemplary embodiment of the invention.

FIG. 2 is a partial end view of a dynamometer torsional dampingapparatus taken along lines I--I of FIG. 1 according to an exemplaryembodiment of the invention.

FIG. 3 is a partial sectional view of the dynamometer torsional dampingapparatus taken along lines II--II of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is an elevational view of a engine dynamometer test arrangement10 including a combustion engine drive shaft 20 interconnected to adynamometer 30 by a dynamometer damping apparatus 100 for measuring avariety of engine performance parameters over a wide range of operatingspeeds and loading conditions. More specifically, an engine 19 thatdrives the drive shaft 20, schematically shown in the drawing is coupledto a flange 21 at an end of the drive shaft 20, and a flange portion 22of the drive shaft 20 is coupled to a drive side of the dampingapparatus 100. An input shaft 32 of the dynamometer 30 is coupled,either directly or indirectly, to an output side of the dynamometerdamping apparatus 100. In the exemplary embodiment, the input shaftflange 32 of the dynamometer is part of a hydraulic hub coupled to thedamping apparatus 100.

Although the exemplary embodiments of the invention are disclosed in thecontext of a combustion engine dynamometer test cell arrangement, theinvention is applicable to dynamometers coupled to any type of rotatingmachinery, which is referred to herein generally as a prime mover. Stillmore generally, however, many of the features, aspects and advantages ofthe invention are applicable to the coupling of any two or morerotatable members, which rotate about a common axis.

FIG. 2 is a partial end view of an exemplary dynamometer dampingapparatus 100 taken along lines I--I of FIG. 1, and FIG. 3 is a partialsectional view taken along line II--II of FIG. 2. The exemplary dampingapparatus 100 includes generally a body plate 200 rotatably coupled to afinger plate 300. The body plate 200 and the finger plate 300 arecooperatively engageable to compress a plurality of spring members 400interconnected therebetween in response to relative rotational movementbetween the body member 200 and the finger plate 300 about a commonrotation axis to dampen torsional stress therebetween.

FIGS. 2 and 3 show an annular antifriction bearing 40 interconnectingthe body plate 200 and the finger plate 300. The body plate incudes ahub portion 220 with an outer circumferential surface 222 protrudingfrom the inner side 202 of the body plate 200, and the finger plateincludes a central bore with an inner circumferential surface 322. Thebearing 40 is retained about the outer circumferential surface 222 ofthe body plate 200 and within the inner circumferential surface 322 ofthe finger plate 300. More specifically, the antifriction bearing 40 hasan inner race retained about the outer circumferential surface 222 ofthe body plate 200 and an outer race retained within the innercircumferential surface 322 of the finger plate 300. The antifrictionbearing 40 is press fit between the body plate 200 and the finger plate300. In the exemplary embodiment, a portion of the annular bearing 40 isretained between a bearing seating surface 224 of the body plate 200 anda first annular bearing retainer 50, and another portion of the annularbearing 40 is retained between a bearing seating surface 324 on thefinger plate 300 and a second annular bearing retainer 60.

According to another aspect of the invention, the circumferentialsurface 222 has a relatively wide axial dimension corresponding to asubstantially complementary axial dimension on the inner circumferentialsurface 322 of the finger plate 300. These relatively wide axialsurfaces 222 and 322 provide for a precise and stable rotationalcoupling between the body plate 200 and the finger plate 300, whereinthe damping apparatus 100 maintains its mechanical integrity over a widerange of rotational speeds and when subjected to relatively largeamounts of torsional stress. In the exemplary embodiment, at least twoadjacent antifriction bearings 41 and 42 interconnect rotatably the bodyplate 200 and the finger plate 300. And according to one embodiment, theantifriction bearings 40 are angular contact bearings, which canwithstand both radial and thrust loads. These exemplary angular contactbearings are available from the Kaydon Bearing Company, Part No.KC047XPO.

FIG. 2 shows the plurality of spring members 400 at least partiallydisposeable in corresponding recesses 210 with opposing end portions 212arranged about the rotation axis on an inner side 202 of the body plate200. FIG. 3 shows an outer ring retainer 500 removably coupled to theinner side 202 of the body plate 200 over the plurality of springmembers 400 for retaining the spring member 400 in the correspondingrecesses 210 of the body plate 200. In the exemplary embodiment of FIGS.2 and 3, the outer ring retainer 500 also includes a plurality ofrecesses 510 with opposing end walls 512 arranged about the rotationaxis. The recesses 510 and end walls 512 of the outer ring retainer 500are alignable with the recesses 210 and end walls 212 of the body plate200, wherein the plurality of spring members 400 are also at leastpartially disposed in the recesses 510 of the outer ring retainer 500and between its end walls 512 when the outer ring retainer 500 iscoupled to the body plate 200.

According to the exemplary embodiment of FIG. 2, the recesses 210 withopposing end walls 212 of the body plate 200 are defined by a pluralityof stop blocks 230 mounted in an annular recess 210 formed in the bodyplate 200. Similarly, the recesses 510 with opposing end walls 512 ofthe outer ring retainer 500 are defined by a plurality of stop blocks530 mounted in an annular recess 510 formed in the outer ring retainer500. According to a related aspect of the invention, the stop blocks 230and 530 are retained in the annular recesses 510 by machine screws 90,which are designed to shear under excessive torque loading conditions asa safety feature. In one applications, the screws shear at approximately3400 ft lbs torque.

FIGS. 2 and 3 show the finger plate 300 including a plurality ofsubstantially outwardly protruding finger members 330 disposed betweenopposing stop blocks 230. The finger members 330 are engageable with theplurality of spring members 400 to compress the plurality of springmembers 400 in response to relative rotation of between the body plate200 and the finger plate 300, wherein the spring members dampentorsional vibration between the body plate 200 and the finger plate 300.FIG. 3 shows the opposing stop blocks 230 and 530 defining a spacetherebetween, wherein the each finger member 330 is positionable andmovable between a corresponding pair of opposing stop blocks duringrelative rotation movement between the body plate 200 and the fingerplate 300. FIG. 2 shows opposing sides of the finger members 330 insubstantial alignment with the end walls 212 and 512 defined by the stopblocks 230 and 530 when the finger plate 300 is in a biased, no loadposition relative to the body plate 200. As a transient torsional loadis applied between the body plate 200 and the finger plate 200, thefinger plate 300 rotates relative to the body plate 200 and the fingersmembers 330 engage and compress the spring members 400, which dampen thetorsional load.

According to another aspect of the invention, the outer ring retainer500 is readily removably coupleable to the body plate 200 to permitadding, removing and interchanging spring members 400 to change thedamping characteristic of the apparatus 100. According to the invention,the plurality of spring members 400 includes at least two spring members400 disposed in corresponding recesses 210 in the body plate 200 asshown in FIG. 2. The exemplary embodiment, however, includes additionalrecesses 210 for receiving additional spring members 400, not shown inthe drawing, wherein the spring members 400 are arranged generallysymmetrically about the rotation axis. The invention also encompassesother embodiments having more than four spring members. The springmembers are generally wire wound coil springs. Each spring member is,for example, rated between approximately 100 and 500 inch-pounds, whichrating may be more or less depending on the particular application. Inone embodiment, the spring members are chrome silicon springs availablefrom Lee Spring Company, Part No. LHL-1000C-12.

In the exemplary embodiment of FIG. 2, an end cap 420 is disposedbetween end portions of the spring members 400 and the end walls 212 and512 of the recesses 210 and 510. The end caps 420 include a hub portion422, which may be press fit within an end portion of the coil springmember, and a base portion 424 engageable with the end walls 212 and512.

According to another aspect of the invention, the spring members 400 arelightly coated with a lubricant to reduce frictional contact between thespring members 400 and the recesses 210 and 510 during movement of thespring members. According to a related aspect of the invention, anannular seal 70 is disposed between an outer circumferential surface 350of the finger plate 300 and an inner circumferential surface 550 of theouter ring retainer 500. The annular seal 70 prevents seepage of anylubricant, which has a tendency to become viscous when heated, out fromthe recesses 210 and 510. In the exemplary embodiment, the annular seal70 is an annular quad-ring available from the Zatkoff Company, Part No.262.

According to another aspect of the invention, an adapter plate 80 isremovably and interchangeably coupled to the outer surface 204 of thebody plate 200 by a plurality of bolts 82 extended through inner side202 of the body plate 200. The adapter plate 80 is coupleable to one ofeither the dynamometer drive shaft flange 32 and the prime mover driveshaft flange 22 by a second plurality of bolts 84. The other of theprime mover drive shaft flange 22 and the dynamometer drive shaft flange32 is coupleable to the finger plate 300 by a third plurality of bolts86. In the exemplary embodiment of FIGS. 1 and 3, a shaft flange 32 ofthe dynamometer 30 is coupled to the adapter plate 80 of the body plate200, and the shaft flange 22 of the prime mover drive shaft is coupledto the finger plate 300.

According to yet another aspect of the invention, the damper apparatus100 weighs between approximately 15 and 20 pounds. This relativelylightweight reduces the load on the dynamometer shaft, which reduceswear on the dynamometer 30. In one embodiment, the body plate 200 ismade from aluminum or some other material, which reduces substantiallythe overall weight of the damping apparatus 100. The finger plate 300and the stop blocks 230 and 530 however are made from a steel materialor some other relatively strong material, which will withstand theforces exerted thereon during operation of the apparatus 100.

While the foregoing written description of the invention enables anyoneskilled in the art to make and use what is at present considered to bethe best mode of the invention, it will be appreciated and understood byanyone skilled in the art the existence of variations, combinations,modifications and equivalents within the spirit and scope of thespecific exemplary embodiments disclosed herein. The present inventiontherefore is to be limited not by the specific exemplary embodimentsdisclosed herein but by all embodiments within the scope of the appendedclaims.

What is claimed is:
 1. A method for damping torsional vibration betweena prime mover and a dynamometer, the method comprising:coupling one ofthe dynamometer and the prime mover to an outer side of a body platerotatable about a rotation axis; coupling the other of the dynamometerand the prime mover to an outer side of a finger plate having aplurality of substantially radially outwardly protruding finger members,the finger plate rotatably coupled to the body plate wherein the fingerplate is rotatable about the rotation axis; engaging the plurality offinger members with an end portion of at least one of a plurality ofspring members, the plurality of spring members at least partiallydisposed in corresponding recesses arranged about the rotation axis onthe inner side of the body plate, opposing end portions of each springmember disposed between and engageable with corresponding end walls ofeach of the corresponding recesses of the body plate; retaining theplurality of spring members in the corresponding recesses of the bodyplate with an outer retainer ring disposed over the plurality of springmembers and removably coupled on the inner side of the body plate; andengaging the finger members with the plurality of spring members tocompress the plurality of spring members in response to relativerotational movement between the body plate and the finger plate aboutthe rotation axis, wherein the compressed spring members dampentorsional stress between the prime mover and the dynamometer.
 2. Themethod of claim 1 further comprising disposing the plurality of springmembers at least partially in corresponding recesses in the outerretainer ring when the outer retainer ring is coupled to the body plate,engaging opposing end portions of each spring member with correspondingend walls of each corresponding recess in the outer retainer ring, theend walls in the body plate aligned opposite the end walls in the outerretainer ring and defining a space therebetween, and moving the fingermembers between opposing end walls to compress the spring members duringrelative rotational movement between the body plate and the fingerplate.
 3. The method of claim 2 further comprising defining thecorresponding recesses of the body plate by a plurality of spaced stopblocks mounted in an annular recess formed in the body plate, anddefining the corresponding recesses of the outer retainer ring by aplurality of spaced stop blocks mounted in an annular recess formed inthe outer retainer ring.
 4. A method for damping torsional vibrationbetween a prime mover and a dynamometer, the method comprising:couplingone of the dynamometer and the prime mover to an outer side of a bodyplate rotatable about a rotation axis; coupling the other of thedynamometer and the prime mover to an outer side of a finger platehaving a plurality of substantially radially outwardly protruding fingermembers, the finger plate rotatably coupled to the body plate whereinthe finger plate is rotatable about the rotation axis; engaging theplurality of finger members with an end portion of at least one of aplurality of spring members, the plurality of spring members at leastpartially disposed in corresponding recesses arranged about the rotationaxis on the inner side of the body plate, opposing end portions of eachspring member engageable with corresponding end walls of each of thecorresponding recesses of the body plate; and engaging the fingermembers with the plurality of spring members to compress the pluralityof spring members in response to relative rotational movement betweenthe body plate and the finger plate, wherein the compressed springmembers dampen torsional stress between the prime mover and thedynamometer.
 5. The method of claim 4 further comprising rotatablyinterconnecting the body plate and the finger plate with an antifrictionbearing retained about an outer circumferential surface of a hubprotruding from the inner side of the body plate, the bearing retainedwithin an inner circumferential surface of the finger plate.
 6. Themethod of claim 4 further comprising coupling the body plate to one ofthe dynamometer and the prime mover with an adapter plate removablycoupled to the outer side of the body plate.